Observability Analysis of INS Rapid Transfer Alignment

An observability analysis of the rapid transfer alignment (RTA) of the inertial navigation system (INS) is presented in this paper. RTA is divided into the time-invariant system and time-varying system to be analyzed. When there is not rotation between the body frame and navigation frame, or the sensed specific force of slave inertial navigation system (SINS) is constant, RTA is a time-invariant system and has three unobservable states. Moreover the three misalignments are not estimated at the same time. When RTA is a time-variant system, it will be instantaneous observable by appropriate maneuver, which is easily achieved. With the level constant velocity maneuver, RTA is similar to a time-invariant system. So it has three unobservable states. With the level turn maneuver, RTA is instantaneous observable if the rotation angular rate is non-constant. With the marine sway maneuver and wing-rock maneuver, RTA is observable. The result of the investigation shows that appropriate maneuver, which is non-constant acceleration and/or rotation with non-constant angular rate, will enhance the observability of RTA easily.